In a typical cellular radio system, wireless terminals (also referred to as user equipment unit nodes, UEs, and/or mobile stations) communicate via a radio access network (RAN) with one or more core networks. The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a radio base station (also referred to as an RBS, a base station, a RAN node, a “NodeB”, and/or enhanced NodeB “eNodeB”). A cell area is a geographical area where radio coverage is provided by the base station equipment at a base station site. The base stations communicate through radio communication channels with wireless terminals within range of the base stations.
A wireless terminal generates transmission data to be transmitted to a radio base station during one or more transmission time intervals, and when the wireless terminal generates transmission data more quickly than it can be transmitted, the transmission data is queued in a transmit buffer for transmission during a subsequent Transmission Time Interval(s) or TTI(s). The base station, for example, may designate a Transport Format Combination TFC (e.g., an E-DCH transport format combination or E_TFC) that defines a data rate for the wireless terminal, and the designated transport format combination TFC may thus define a number of data bits that may be transmitted by the wireless terminal during a TTI. A higher TFC thus allows the wireless terminal to transmit a greater number of data bits during a TTI, and a lower TFC restricts the wireless terminal to transmitting a lesser number of data bits during a TTI.
In addition to the data bits, the wireless terminal may also transmit a buffer indicator bit, such as a happy bit, each TTI. A happy bit is defined, for example, by the 3GPP (3rd Generation Partnership Group) standard, 3GPP TS 25.321, V11.0.0, MAC protocol specification, version, Release 11, sections 9.2.5.3.1 and 11.8.1.5, December 2012. The happy bit is included on the E-DPCCH (E-DCH Dedicated Physical Control Channel) for every E-DCH (Enhanced Dedicated Channel) transmission on each Activated Uplink Frequency, RRC (Radio Resource Control) configures MAC (Medium Access Control) with a Happy_Bit_Delay_Condition over which to evaluate a current grant relative to the TEBS (Total E-DCH Buffer Status) after application of an E_TFC (E-DCH Transport Format Combination) selection procedure. More particularly, the Happy_Bit_Delay_Condition (HBDC) may be defined as the product of a happy bit delay, in seconds or milliseconds, and the bit-rate according to a current E_TFC in bits/second, or equivalently as the product of a number of transmission time intervals (nTTI) and a number of bits transmitted during one TTI according to a current E_TFC, such that the Happy_Bit_Delay_Condition (HBDC) is equal to nTTI*ETFC.
For every E-DCH transmission and for each Activated Uplink Frequency, the Happy Bit on a frequency is set to “unhappy” if all of the three following criteria are met on that frequency:                (1) The wireless terminal (UE) is transmitting as much scheduled data (defined by E_TFC) as allowed by the current Serving_Grant on that frequency; and        (2) The wireless terminal (UE) has enough power available to transmit at a higher data rate on that frequency; and        (3) The amount of data in the wireless terminal transmit buffer exceeds the Happy_Bit_Delay_Condition (HBDC) defined as HBDC=nTTI*E_TFC so that the wireless terminal transmit buffer cannot be emptied in a time (e.g., a number of TTIs) specified by nTTI at a current data rate (e.g., a number of bits per TTI specified by the current Transport Format Combination or E_TFC).        
For example, a value of the HBDC may take one of 8 values between (and including) 2 milliseconds (ms) and 1000 milliseconds (ms), and these HBDCs may be mapped to values of nTTI. For example, values of nTTI (a number of TTIs) may take one of eight values including: 1 corresponding to a 2 millisecond delay condition; 5 corresponding to a 10 millisecond delay condition; 10 corresponding to a 20 millisecond delay condition; 25 corresponding to a 50 millisecond delay condition; 50 corresponding to a 100 millisecond delay condition; 100 corresponding to a 200 millisecond delay condition; 250 corresponding to a 500 millisecond delay condition; and 500 corresponding a 1000 millisecond delay condition. The HBDC, nTTI, and/or an indicator thereof may be transmitted from the radio base station to the wireless terminal as the communication/call/session/link is set up (e.g., as the wireless terminal enters a CELL DCH state or CELL dedicated channel state) in accordance with the RRC (Radio Resource Control) specification.
The wireless terminal can thus calculate the Happy_Bit_Delay_Condition (HBDC) as HBDC=nTTI*E_TFC (using nTTI and E_TFC values provided by the base station), and the wireless terminal may determine the happy bit value for each TTI based on whether a current amount of data in the transmit buffer exceeds HBDC or not. Stated in other words, the wireless terminal can calculate a number of bits that may be transmitted over a period of time specified by the current HBDC calculated as nTTI*E_TFC (effectively, a product of a time period and a bit-rate).
The buffer indicator bit (e.g., the happy bit) may be used by the base station to make scheduling decisions for the wireless terminal as follows: increase or maintain E_TFC (the number of bits transmitted by the wireless terminal during a TTI) if the wireless terminal transmits an unhappy bit; or decrease E_TFC (the number of bits transmitted by the wireless terminal during a TTI) if the wireless terminal transmits a happy bit or a series of consecutive happy bits.
Additionally, scheduling information may be transmitted from the wireless terminal to the radio base station over an E-DCH in accordance with 3GPP TS 25.321, V11.0.0, MAC protocol specification, Release 11, sections 9.2.5.3.2 and 11.8.1.6, December 2012, along with a regular data transmission(s). The scheduling information may be transmitted periodically (as configured by the RRC specification when the connection is set up) and/or opportunistically in bits that would otherwise by unused or spare. The scheduling information may include 18 bits as follows:                (1) Highest priority logical channel ID (HLID)=4 bits;        (2) Total E-DCH Buffer Status (TEBS)=5 bits;        (3) Highest priority Logical channel Buffer Status (HLBS)=4 bits; and        (4) UE Power Headroom (UPH)=5 bits.        
The scheduling information thus includes more detailed information defining the status of the transmit buffer (the Total E-DCH Buffer Status or TEBS) and the power available to the wireless terminal (UE Power Headroom or UPH) than may be available from a happy bit. The scheduling information, however, may be transmitted less frequently than the happy bit because the scheduling information consumes greater bandwidth that could otherwise be used for data transmission. Stated in other words, each transmission of the scheduling information may consume 18 bits of an uplink transmission that could otherwise be used to transmit data thereby reducing an effective bit rate for uplink transmissions from the wireless terminal to the base station.
Accordingly, there continues to exist a need to provide improved scheduling of transmissions in a wireless network.